Gear pump



July 27, 1965 Filed Dec. 15, 1962 J- F. HOFFER GEAR PUMP 4 Sheets-Sheet1 Fig.

INVENTOR.

July 27, 1965 J. F. HoFFER 3,196,800

GEAR PUMP Filed Dec. 13, 1962 4 Sheets-Sheet 2 1N VEN TOR. WMU f #af/ff?y W www J. F. HOFFER `luly 27, 1965 GEAR PUMP 4 Sheets-Sheet 5 FiledDec. 13, 1962 INVENTOR J. F. HOFFER July 27, 1965 GEAR PUMP 4'Sheets-Sheet 4 Filed DeG. 13, 1962 w J. 4 if WQ f A f M//a WF 1 N VENTOR. JAI/W5 E ,wf/f5? United States Patent O ddtltl .llames F. Hoffen',Redondo Beach, Calif., assigner to Parlrer-Hannitin tiorporation,Cleveland, (Ehio, a corporation of @hier Filed Dec. l, W62, Ser. No.Weit-7 25 Claims. (Ci. 10S-426) This invention relates to gear pumps andmore particularly to gear pumps of the cartridge type in which thecartridge comprises a set of plates forming a pumping chamber whichcontains the gears, the cartridge being mountable in a main housingwhich provides a driving connection and fluid inlet and outlet ports.

Cartridge type gear pumps may be of either fixed clearance or pressureloaded type. In the fixed clearance type end plates are fitted againstthe sides of the gears with a small predetermined or fixed clearancetherebetween for sealing the side faces of the gears without having theplates in actual contact therewith. Thus there is only fluid friction onthe gear faces as the gears rotate and there is relatively small loss ofinput power duc to friction losses. However, the clearance is a uidleakage path which affects the volumetric etiiciency of the pump, andobviously, the greater the clearance the greater the leakage and thelower the volumetric efficiency. Thus it is desirable in highperformance pumps to keep the clearance very small.

When the clearance becomes very small other problems are encountered.Thus localized or unequal heating or cooling of the plates and gears maycause expansion or contraction of the parts so as to take up theclearance and bring the plates and gear side faces into direct contact.This will not only reduce mechanical efficiency but is very apt to scoreor bind the parts so as to seriously damage or destroy the pump.

In high performance pumps, such as used for missiles and space craftwhere pressures may be as high as 3G00 p.s.i. and rotative speedsupwards of 60,09() rpm., the problem becomes acute. The initialclearances must be very small to provide the volumetric eiiiciencyrequired and the high pressures and speeds quickly cause localizedheating and differential expansion of parts tending to tal/ie up suchclearances.

In pressure loaded pumps the end plates are yieldably pressed againstthe gear side faces so that there is no predetermined or fixedclearance. This results in less leakage and high volumetric efficiencybut has the disadvantage `of lower mechanical efficiency because of thegreater friction loss due to the gear side faces rubbing against the endplates. Friction losses are minimized as far as possible by applyingjust enough pressure on the end plates to press them against the gearswith enough force to keep the parts from separating and not enough forceto cause excessive friction and wear between the parts. However, whendifferential expansion or contraction of the gears or plates occurs theplates must be able to quickly move in a direction toward or away fromthe gears, as the case may be, in order to retain contact therewith andto maint-ain such contact without excessive pressure or friction betweenthe parts.

Fixed clearance pumps are generally more suitable for low pressureoperation because leakage through a given clearance is less than at highpressures and becomes a lgbhh Patented July 27, 1965 ICC minor factor,and also because friction losses between the gear side faces and the endplates must be minimized since they are a relatively large percentage ofthe input power for driving the pump. Conversely, pressure loaded pumpsare generally more suitable for high pressure operation because leakagepast the gear side faces becomes a more important factor and isminimized by eliminating the clearance. Friction losses, on the otherhand, become ess important since `they are a smaller percentage of theinput pov'e.

lt is an object of the present invention to provide cartridge type gearpumps of either the fixed clearance or pressure loaded form in which theend plates can quickly move in axial directions without appreciablemechanical or frictional resistance to compensate for thermal expansionor contraction of the parts in such a manner that in fixed clearancepumps the clearance remains substantially constant and in pressureloaded forms the contact pressure between the plates and gear side facesremains substantially constant.

Another obiect is to avoid bolts or other mechanical means for clampingthe end plates in position next t0 the gear side faces in the fixedclearance pumps, as has heretofore been the practice, but to utilizehydraulic forces only for 'this purpose, such hydraulic forces beingcarefully controlled and distributed so that the plates may move ineither axial direction without radial displacement and without tilting.

Another object is to provide a cartridge type gear pump of either theiixed clearance or pressure loaded type in which the end plates areaxially aligned with each other by dowels extending laxiallytherethrough, the plates being symmetrically formed and hydraulicallybalanced in such a manner that the plates cannot move sideways or tiltso as to bind upon the dowels as this would interfere with the freeaxial movement of the plates axially `along the doweis when compensatingfor differential expansion or contraction between the gears and plates.

lt is another obiect to provide a cartridge type gear pump of either thefixed clearance or pressure loaded form in which the cartridge endplates are axially aligned by dowels passing therethrough and in whichthe plates are so balanced against forces tending to radially displaceor to tilt the that side loading of the plates upon the dowels isavoided whereby the dowels may be anchored in the housing at only oneend thereof, thus greatly facilitating manufacture and assembly of thepump by :making it unnecessary to provide opposed recesses aligned to ahigh degree of accuracy for receiving both ends of the dowels.

Another object is to provide a fixed clearance type gear pump in whichan end plate is urged tow-ard the gear side faces by controlled fluidpressure means, the plate being engaged by a stop to provide apredetermined clearance with the gear side faces, and with the platebeing movable ragainst the action of the fluid pressure means uponmomentary differential expansion or contraction of the parts which takesup the clearance whereby the pump at that time will operate as apressure loaded type without excessive frictional contact between thegear side faces and plates such as would bind or damage the parts.

Another object is to provide pumps of the types described in which apair of end plates have opposed recesses to form a pumping chamber, theplates having opposed faces with a sealing means therebetween forsealing the pumping chamber.

Another object is to provide cartridge type gear pumps of either the xedclearance or pressure loaded form in which a pair of end plates haveopposed recesses for receiving the gears and the plates are maintainedin proper axial position with respect to the gears by fluid pressure.

Other objects of the invention will be apparent from the drawings andfrom further description.

Generally described, the invention provides a cartridge insertable intoa main housing. The cartridge includes two end plates, each of which isrecessed for receiving one-half the axial length of'a pair of gears. Inthe xed clearance type, the end plates butt against each other t provideinitial fixed clearances of predetermined dimension between the gearside faces and the bottom walls of the recesses. In the pressure loadedform, the bottom walls of the recesses contact the gear side faces andthere is a slight clearance between the plates where they surround thegears.

The plates are aligned axially with respect to each other by dowelsextending through the plates and having one end anchored in recesses inthe housing for locating the angular position of the plates within thehousing. The gears have shafts extending from either side thereof, theshafts having bearing support in openings in the plates. One plate issupported endwise by the body and the other plate is pressed toward thefirst mentioned plate by hydraulically actuated pistons or buttons whichare so located and dimensioned that they not only eounterbalance axialforces tending to separate the plates from the gears but also compensatefor tilting forces applied to the plates. This, plus the face that theplates are symmetrically formed and so balanced that there is notendency for the same to move sidewise with respect to the dowels,prevents side loading between the plates and dowels. As a result, theplates may move axially with respect to the dowels without appreciableinterference due to friction or binding thereon so as to freelycompensate for expansion or contraction of the gears or plates tomaintain substantially the same clearance between the gears and platesin the case of fixed clearance pumps and to maintain substantially thesame contact pressure between the gears and plates in the case ofpressure loaded pumps.

In the drawings:

FIG. 1 is a side view, partly in vertical axial cross section,

FIG. 2 is a section view along the lines 2-2 of FIG. l,

FIG. 3 is a section view along the lines 3-3 of FIG. 1,

FIG. 4 is a section view along the lines 4-4 of FIG. 1 but with thecartridge unsectioned,

FIG. 5 is an end view,

FIG. 6 is a fragmentary section view along the lines 6-6 of FIG. 3 withthe cartridge shown partly sectioned and partly unsectioned,

FIG. 7 is a fragmentary section view along the lines 7--7 of FIG. lshowing in exaggerated manner the clearances between the cartridge endplates and the side faces of the gear in the fixed clearance form of thepump,

FIG. 8 is a view similar to FIG. 7 but showing in exaggerated manner theclearance between opposed faces of the end plates in the pressure loadedform of the pump,

FIG. 9 is a view along the lines 9-9 of FIG. 1 but with the inner end ofthe end plate formed with a groove and a sealing element fitted withinthe groove, and

FIG. 10 is a fragmentary cross section along the lines 10-10 of FIG. 9showing the groove and sealing element.

The pump has a main housing 10 comprising a body 11 having a cylindricalbore 12 therein which is closed at one end by a head structure 13 andwhich is closed at the other end by a cap 14 removably attached to body11 by bolts 15 and sealed with respect to the body by a resilientsealing ring 16.

Cap 14 has a fluid inlet port 17 and a fiuid discharge port 18. Aportion of the latter is enlarged as at 19 to receive an annular portsealing piston or button 20 which has a discharge opening 21therethrough in communication with enlarged bore portion 19. Button 20is sealed with respect to bore portion 19 by a resilient sealing ring 22and is pressed toward body bore 12 by spring 23.

Mounted within bore 12 is a cartridge assembly, gcnerally designated 25,which includes a pair of plates 26, 27, a pair of gears 28, 29 and apair of dowel pins 30, 31.

Plates 26, 27, have opposed recesses 34, 35, therein of equal depthwhich from a pumping chamber, generally designated 36 for receivinggears 28 and 29. The gears are in mesh with each 'other and have arunning fit with portions of radially outer walls 38, 39 of recesses 34,35, respectively.

Adjacent to radial outer walls 38, 39 the plates have opposed llatraised surfaces or ribs 40, 41. These ribs normally contact each otherin the fixed clearance form of pump, as shown in FIG. 7, to closepumping chamber 36, there being very small clearances 42, 43 betweenbottom walls 44, 45 Iof the plates and the adjacent side faces 46, 47 ofthe gears. In the pressure loaded form of pump, as shown in FIG. S,there is a slight clearance 49 between ribs 40, 41 when the gear sidefaces 46, 47 are in contact with bottom walls 44, 45 of the recesses inthe plates. Ribs 40, 41 surround the entire pumping chamber 36 exceptwhere the latter is intersected by an inlet opening.

Rib 41 is identical to rib 4t). Both are narrow for good sealing contactwith each other and for keeping to a minimum the area therebetween whichis subject to fiuid pressure gradient.

Spaced from and co-planar with rib 40 are additional flat raisedsurfaces 511, 51 on plate 26 with a channel 52 between rib 41) andraised surfaces 50, 51. Plate 27 likewise has raised surfaces S3, 54spaced from and coplanar with raised rib 41 with a channel 54a betweensuch rib and surfaces.

Channels 52, 54a communicate freely with an annular clearance 55 betweenthe outer periphery of plates 26, 27 and the wall of bore 12, and alsocommunicate with aligned low pressure inlet passages 56, 57 in plates 27and 26 respectively, passage 57 being in register with inlet port 17.

Gear 28 has shafts 6i), 61 integral therewith, such shafts havingbearing support or contact with openings 62, 63 in plates 26, 27. Theshafts are hollow and have a spline section 64 therein for receiving thesplined end 65 of a drive shaft 66. Shaft 66 has an external portion 67for connection to a motor for driving the pump.

Gear 29 is identical to gear 28 and likewise has integral shafts 70, 71in bearing contact with openings 72, 73 in plates 26, 27 and there is aspline portion 74 which is utilized in the event cartridge 25 and cap 14are assembled in a rotative position with respect to body 11 for thepurpose of using reverse direction of rotation of shaft 66.

Dowels 30, 31 extend through both plates 26, 27 with a snug but slidingfit to axially and angularly align the same with respect to each other.One end of each dowel extends beyond the other face of plate 26 and intoopenings 77, 78 in head portion 13 of body 11 for locating the plates26, 27 angularly within body 11. Plates 26, 27 also have openings 79, 30and counterbores 81, 82 therein which serve to provide opencommunication between low pressure areas 12, 52, 54a and opposite sidesof housing bore 12 for equalizing the pressure therein.

Passages 56, 57 communicate with clearance 55 and with the ends of bore12 by means of cutouts 68, 69 in plates 26, 27. Inlet passages 56, 57intersect bores 53, 59 which in turn intersect recesses 34, 35 in theplates to form an inlet or low pressure portion, generallydesigs,19a,soo

mit nated d, of pumping chamber 36 which is exposed to gears 2S, 29 onone side of a plane passing through the axis of the two gears. On theother side of such plane plate 25 has a bore S6 extending part waythereinto from recess 34. @pposite bore $6 is a bore 37 in plate 27which intersects recess 35 also intersects a bore 88 which is slightlyoffset therefrom.

Bore extends through the plate to the outer surface 39 thereof and inregister with opening 2l through button Ztl. The latter bears on surface39 to seal passages S3 and 2l from the interior of body bore l2 and alsoto help provide force for holding plates Z6, 27 in position with respectto the gears, as is hereinafter further described. Button Ztl is heldagainst surface 89 by spring 23 plus the effect of huid pressure incounterbare 19 acting on the outer end of the button.

The outer end area of button 2li exposed to high pressure fluid incounterbore i9 is larger than the area of the other end of the buttonwhich is in contact with plate surface 59 so that the iluid pressuregradient across the inner end of the button can never unseat the buttonfrom plate surface 39.

Bores 3d, S7, together with the portions of recesses 34, 35therebetween, provide a high pressure zone, generally designated S5, ofthe pumping chamber and fluid therein at ull discharge pressure isexposed to adjacent portions of the two gears and to the adjacentportions of outer radial walls 3S, 39 of the pumping chamber.

As shown in FlG. 3, openings 62 in plate 26 has a lubrication groove 9%at one side thereof running throughout its length and there are drilledpassages 9i, 92 connecting groove Sill with inner raised face 5l of theplate. Likewise, opening 72 has a lubrication groove 93 which isconnected by drilled passages 94, 95 with the inner face oi plate 2J. Inlike manner, and as shown in FIG. 9, opening 63 in plate 27 haslubrication groove 9S connected by drill passages 99, ltlll with innerface portion 5d and opening 73 has a lubrication groove lill connectedby drill passages E92 and ill with inner face portion S4. Passages 92and 10i) register with each other and passages 95, 193 register witheach other whereby groove 9h is connected with groove 9S and groove 93is connected with groove lill to provide approximately equal flow ofhuid through such connected grooves for substantially equallylubricating and cooling the gear shafts in their bearings.

Grooves 99, 93, 9S and lill are also open to the low pressure clearancespaces at the outer ends of the cartridge, these clearance spaces beingin turn open to clearance 55. ln addition to supplying lubricant to thegear shaft bearings, grooves 9d, 93, 93 and lill also serve to preventbuild-up of pressure in undercuts li, ldd, 107 and ldd by fluid leakingpast the gear side faces and bottom walls of recesses 34, 35 by ventingsuch undercuts to low pressure areas of the pump.

Plate 27 has passages Mil, lll, 1l2 and U3 therethrough connectingrecess 35 at points traversed by the gear teeth and the gears rotatewith the outer end tace 89 of the plate where they register withopenings through respective annular pistons or buttons lll, llo, 117 andlid located in recesses lll?, lill, iZl and 122 in cap le. Each of thebutttons is constantly urged toward plate 27 by a spring such as M3 andis sealed with respect to its respective recess by a packing such as3124. Fluid under pressure from recess 35 passes through the buttons andacts upon the rear face thereof to press the buttons into sealingengagement with end face il@ of plate Z7. ,The inner end of each buttonhas a reduced diameter face, similar to that of button Ztl, to present asmaller area of contact against plate Z7 than the area or the rear faceso that there is always an overbalance area acted upon by iuid pressurefor mintaining leak-proof abutment of the buttons against plate 27.

ln operation, shaft da is rotated in a clokwise direction as viewed inFlG. 2. This causes gears 28 and 29 to rotate as indicted by the arrows.Jluid under low pressure entering port i7 passes through passage 56 intolow pressure chamber 43 where it is picked up by the rotating gears andcarried in the gear pockets to be discharged under high pressure intohigh pressure chamber 3S and through bore 87, passage 33 and bore 2l ofbutton 2@ to be discharged through outlet port itil. Spring 23 and thepressure of the fluid in outlet bore portion 19 acting on the rear faceof button 20 presses the latter into sealing engagement with end face 89of plate 27 to seal the high pressure lluid from bore l2 exteriorly ofplates 26, Z7.

As the gears rotate and high pressure is developed in chamber 35 therewill be some leakage past the radially outer edges and side faces of thegear teeth as the teeth approach chamber d5 so that fluid within thegear pockets that are closed by radially outer walls 38, 39 of thepumping chamber gradually takes on a higher and higher pressure as thetooth pockets approach high pressure chamber 85. Thus, as given toothpocket sweeps across low pressure chamber i3 it becomes lled with luidat low pressure. When the pocket is closed olf by walls 38, 39 thepressure of the huid therein gradually increases as the pocketapproaches high pressure chamber due to leakage past the gear teeth fromthe direction of high pressure chamber S5. T he iiuid pressure gradientbetween walls 3S, 39 and *he outer ends of the gear teeth, plus thefluid pressures within the closed gear teeth pockets and within chamberimpose radial loads upon the gears tending to force the same generallytoward the low pressure side of the pump. There are, of course, lesserand oppositely acting side loads on the gears from the low pressure sideof the pump but the net eliect is to impose side loads on the gearstending to move them away from the high pressure side of the pump. Thesenet side loads are transmitted by the gear shafts to plates 26, 27 atbearing contact points in openings 62, d3, 72 and 73. On plates 26, 27the side loads are counterbalanced in radial directions by the pressureof fluid acting on outer walls 3S, 39 of recesses 34, 35 in plates 26,27. Thus the side or radial loads imposed upon plates 26, 27 arebalanced so that there are no forces acting internally of the platestending to move the plates transversely of the housing. Likewise, lowpressure fluid has access to the complete outer periphery of plates 26,27 so that there are no unbalanced forces acting externally on theplates tending to move the same transversely of the housing. As a resultof such internal and external balancing of radial forces acting on theplates, there are no side loads imposed by the plates upon dowels 3),Si.

The fluid pressures within recesses 34, 35 act in directions upon plates26, 27 tending to axially separate them from each other. This separatingpressure is greater on the high pressure side of the pump than on thelow pressure side so that these pressures also tend to tilt the plateswith respect to each other, that is, to separate them more on the highpressure side than on the low pressure side.

lin addition to the tendency for the plates to tilt because of thehigher axial torce applied to the plates on the high pressure side thanon the low pressure side, there is another set of forces acting on eachplate also tending to tilt the same and acting so as to augment the rstmentioned tendency to tilt. Thus, the fluid pressures within platerecesses 3ft, 3S which act in radial outward directions on walls 38, 39impose a net force on such walls generally in the direction of the highpressure side of the pump, whereas the net counteracting bearing loadsapplied to openings 62, 63, 72 and 73 act on the plate in an oppositedirection and at points axially otset from the net duid pressure forceacting on Walls 38, 39. Since these net forces are opposite and axiallyoffset, they apply a tilting force to the plates which tends to separatethe plates on the high pressure side and bring them together on the lowpressure side. Since the forces are opposite and equal there is notendency for the plates to shift radially.

The forces tending to axially separate and to tilt the plates arecounteracted by buttons 20, 115, 115, 117 and 11S. The force applied byeach button is proportional to the force tending to separate and tiltthe plates and acting in the vicinity of the particular button. Thusbuttons 116 and 118, which are on the low pressure side of the pump,receive their iiuid through passages 111 and 113, respectively. Thesepassages are exposed to tooth pockets toward the low pressure side ofthe pump and generally opposite the particular button. The fluidpressures tending to separate the plates in these areas are relativelylow and therefore the iiuid pressure behind each button 116 and 118 islikewise relatively low. The net area of these buttons acted upon bythis iiuid for urging the buttons toward the plates, that is, the areaof the outer end face of each button between the hole through the buttonand the projected outside diameter of the packing ring, is selected soas to provide a force somewhat greater than necessary for'counterbalancing the axial separating forces on the portions of theplates served or counterbalanced by the particular buttons less aproportionate part of the force with which the plates tend to be broughttogether in this region as a result of the tendency for the plates totilt.

In like manner buttons 115, 117 on the high pressure side of the pumpreceive uid pressure through passages 110, 112 which intersect thepumping chamber in regions where the iiuid pressure in the tooth pocketsis relatively high and thus the fluid pressure behind such buttons isalso relatively high. Button is exposed to full discharge pressure incounterbore 19. The area of each of these three buttons 115, 117 and 20acted upon by iiuid pressure urging them toward the plates is soselected that the buttons press against plate 27 with a force somewhatgreater than necessary for counterbalancing the axial separating forceson the corresponding portions of plates 26, 27 plus a force forcounterbalancing the separating force applied to these portions of theplates due to the tendency of the plates to tilt.

With all of the axial separating and tilting forces on the platescounterbalanced by the buttons in the manner just described, the plateswill have substantially uniform contact pressure at all points of theirmeeting faces or ribs 40, 41 in the case of the fixed clearancearrangement of FG. 7.

Since recesses 34, 3S are of equal depth and of like size and shape, theradial and tilting forces acting on the plates are identical andopposite. It is important that they be so because the force applied toplate 27 by the buttons to oppose tilting is also transmitted to plate26. If the recesses were of diierent depth, size or shape, the tiltingforce on one plate would be dilerent than on the other plate andbalancing of the force on one plate by means of the buttons would notresult in balancing of the forces on the other plate and the unbalancedplate would impose side loads on the dowels. Also, the radial loads oneach plate would be unbalanced and result in side loads on the dowels.With both plates balanced radially and counterbalanced against tiltingforces, as described, there is no appreciable side load or binding uponthe dowels.

In the xed clearance type pump ribs 40, 41 normally remain in contactand the side faces of the gears are normally out of contact with thebottom wall of the recesses so as to maintain clearances 42, 43. Whentemperature changes occur in a manner for momentarily taking upclearances 42, 43 the gears will contact the plates but will not bindthereagainst since plate 27 will move slightly in a direction away fromthe gears against the holding force of the buttons, there being aclearance 138 between plate 27 and cap 14 to permit such movement. Inprior forms of xed clearance pumps in which the end plates aremechanically clamped or bolted in position next to the gears, theclamping or bolting prevents such outward movement of the end plate andhence the clearances must be sufficiently large to permit anydilierential expansion or contraction which is apt to occur if the pumpis to be protected against binding and other damage. Since the plates inthe present invention may move away from the gears as described, thefixed clearances may be very small, as for example from .0002 to .0005"total for both sides, or they may even be zero, without danger of damagebeing done to the pump. During the intervals in which clearances 42, 43are taken up and the gear side faces contact the plates, ribs 40, 41 maybe separated slightly and the pump will function as a pressure loadedtype with the plates pressing against the gears with controlled forcefrom the buttons.

At no time in either the fixed clearance or pressure loaded forms, willthe plates be moved in a direction axially away from the gears by fluidpressure, they are always either in contact with each other at ribs 40,41 or in contact with the gear side faces. Moreover, ribs 40, 41 aresuliiciently narrow so that changes in fluid pressure gradienttherebetween as the ribs move toward or away from each other, in eitherfixed clearance or pressure loaded types, do not prevent the buttonsfrom maintaining the plates in contact with each other or with thegears, as indicated.

1t is important that plate 27 be able to move freely axially alongdowels 30, 31 in the manner just described and at no time should thedowels offer frictional resistance to such movement. This is especiallytrue in ultra high speed pumps as required for missile and space vehicleapplications since such high speeds can induce extremely rapiddifferential thermal expansion and contraction and the plates mustrespond extremely rapidly with compensating sliding movement in order toprevent binding of the gears against the end plates and consequent pumpfailure. By balancing out the radial and tilting forces on the plates asherein described there are no appreciable side loads imposed between theplates and dowels and hence no appreciable frictional resistance toaxial movement of the plates.

It may be noted that the pressure of the gear shafts against the bearingsurfaces of the plates in openings 62, 63, '72 and 73 does not offerappreciable frictional resistance to axial movement of the platesbecause of the fact that the shafts are rotating within such openings.

Since plate 26 butts against an inner transverse wall of head y13, it isapparent that when it shrinks or expands in axial length its one endremains :against the wall of head 13 and ythe axial shortening orlengthening is reflected at the end adjacent the gears. Such `axialshortening and lengthening results in axial sliding movement withrespect to dowels 30, 131 :and thus it is important tha-t it also haveno side loading or binding upon the dowels which would interfere l`withsuch axial sliding. Since it is necessary for both plates to be freelymovable upon the dowels it is important that recesses 34, 35 be o'f likedepth, size and shape so that Itilting forces will be identical and maybe simultaneously count-erbalanced by the action of the buttons, asdescribed.

In the pressure loaded arrangement of FIG. 8, the buttons cause platesy26, 27 to press against the gear side faces with a selected force `thatis proportional to the output pressure of the pump. When expansion `orcontraction of the gears and/.or plates occurs the buttons and plate 7'will move `in a direction toward or away from plate 26 and :a slightincrease or decrease in clearance 49 will result. Upon reversal of theconditions inducing this action the direction of movement of the buttonsand plate 27 will likewise reverse and the predetermined minuteclearance 49 will again be established.

Thus in the FIG. 8 form it is likewise important that the plates befreely axially movable on the dowels for rapid response to the changingconditions so that the pump may continue to operate efficiently andwithout damage. This form is preferred for pump discharge pressures ofover 1,500 psi. Clearance 49 is kept very small so Ithat leakagetherethrough is minor, it being less than 3,19e,eoo

it would be through a like clearance at the side face of the gear sinceleakage between stationary parts is less than between relatively movingparts when the clearances are of equal size.

In the form of the invention illustrated by FIGS. 9 and 10, the raisedrib 40a on plate 27 is provided with a groove 136 in which a flexiblesealing member 13d is located `thus providing an auxiliary Iseal inaddition to the seal formed by the ribs. Preferably, groove 130 isformed with 4one vertical wall '132 and `a tapered Wall i133, Wall 132being vertical to keep the width of the groove lto a .minimum and wall'1-33 being tapered to pro- -vide a Wedge shaped space in-to whichsealing member n311 may be tightly forced by fluid pressure from pumpingchamber recess 35. Groove 130 is 'of a depth slightly greater than thecorresponding dimension of the sealing member so that the latter doesnot contact the bottom of the groove.

Although several forms of the invention have been shown and described,it is obvious that many other modiiications may be made Within the scopeof the invention yas defined 'by the claims.

I claim:

11. A pump comprising a housing, iirst and second plates within saidhousing and having opposed recesses therein forming a pumping chamber,means supporting said plates in said housing, .at least one of saidplates being axially movable relative tothe other, inlet and outletpassages in communication with said pumping cham- Iber, rotary pumpingmeans in ISaid pumping chamber operative when rotated for forcing huidfrom said inlet passage to said outlet passage, and fluid pressure meansforcing said one of said plates axially toward the other.

E2. A pump in accordance with claim l1 in which there is an auxiliarysealing means surrounding at lea-st a portion of said pumping chamberand in sealing contact with both said plates.

3. A pump in accordance with claim 1 in which said one of vthe plateshas a groove surrounding at least a portion of the chamber, and asealing member in said groove and in sealing contact ywith both .saidplates.

4. A pump in accordance with claim I3 in which said groove has atapering wall on the low pressure side of said sealing means, saidsealing means being movable by fluid pressure in said chamber intoWedging engagement with said Itapered Wall and the other .of saidplates.

S. A pump in accordance with claim B in which said groove has latapering wall on the low pressure side of said sealing means, saidsealing means being yshaped and dimensioned so as to be normally out ofcontact with the bottom of said groove whereby a greater area of saidsealing means is exposed to the high pressure side thereof, Isaidsealing means being movable by iiuid pressure acting on said area intowedging engagement with said tapered wall tand a surface on the other ofsaid plates.

6. A pump comprising a housing, irst 'and second plates within saidhousing, means supporting said plates Within said housing, said plateshaving opposed recesses -forming .a pumping chamber, a pair of meshedrotatable gea-rs in said chamber, each gear lhaving a running t withsections of the radially outer walls of the recesses so as to divide thepumping chamber into .a high pressure portion and a low .pressureportion, an inlet passage leading to said lo-W pressure portion, anoutlet passage leading from said high pressure portion, said gears whenrotated serving to deliver iluid from said low pressure portion to saidhigh pres-sure portion, and iiuid pressure means for utilizing iiiuidfrom said chamber for urg-ing Ione of said plates axially toward theother for sealing the side faces of the gears.

7. A pump in accordance with claim l6 in which said plates have opposed`faces surrounding a-t least a portion of said pumping chamber, saidopposed faces being normally yheld in contact with cach other by -saidfluid pressure means for closing said chamber, the bottom .Walls of saidrecesses having Ia slight clearance with the side faces of the gears.

. i8. A pump in accordance with claim 6 in which said plates haveopposed faces Isurrounding at least a portion of said pumping chamber,the bottom walls of said recesses being in engagement with said gearside lfaces so as to provide -a lslight clearance between said opposediaces.

`9. A pump in accordance with claim 6 in which there is a dowel meansaxially aligning said plates, said dowel :means having one end onlythereof engaged with the housing for locating the plates radially withrespect to said housing.

it). The pump of claim 6 in which said plates have opposed facessurrounding said recesses, at least one of said faces has a raised rib-adjacent the pumping chamber Iand coopera-ting with said other -face toclose said chamber, said rib defining `an area subject to a pressuregradient of iluid trom said ychamber which .tends .to 4separate saidplates, said r-i'b bei-ng narrow so .as to minimize the area subject tosuch pressure gradient, and a section of said one face outwardly of `therib being connected to .a low pressure zone of said pump and beingspaced from said other face to provide for liree flow of fluid leakingpast said rib to said low pressure zone whereby buildup of iiuidpressure on said faces outwardly of said rib Iis avoided.

l1.1. A pump in .accordance with claim -lll in which said other platehas a raised rib oppose-d to the iirst mentioned rib and cooperatingtherewith to close said chamber.

12. A pump comprising a housing, iirst .and second plates within saidhousing, means supporting said plates within said housing, said plateshaving opposed recesses forming a pumping chamber, first and secondopenings through the bottom -walls of each recess, a pair of meshedrotatable gears in said chamber 4and having a running it with sectionsof the radial-ly outer walls of the recesses so as t-o divide thepumping chamber into a high pressure portion and la l-ow pressureportion, said gears when rotated serving to deliver fluid from lthe lowpressure portion to the high pressure portion, means for utilizing fluidfrom said high pressure portion for urging one of said plates axiallytoward the other for closing said pumping chamber, said gears havingshafts in bearing contact with the Walls of said openings fortransmitting to said plates radial loads impressed upon said gears byiiuid in said chamber, the radially out-er walls of said recesses beingsubject to radial loads from uid in said chamber so as tocounter-balance the radial loads applied to said plates by said shafts,said recesses being symmetrical and of equal depth and said gearsextending into said recesses equal distances lwhereby the radial loadstransmitted by the gear-s and by tluid pressure in said chamber are thesame on both plates.

13. A pump comprising a housing, iirst and second plates within saidhousing, means mounting sai-d pla-tes within said housing, said plateshaving opposed recesses forming \a pumping chamber, la pair of meshedrotatable gears in said chamber, the sides of said gears having asealing tit with the bottom walls of said recesses and each gear havinga running fit with sections of the radially outer Walls thereof so as todivide the pumping chamber tinto Ia high pressure portion and a lowpressure portion, an Ioutlet passage leading from said high pressureportion, said gears when rotated serving to deliver fluid from said lowpressure portion to said high pressure portion, said gears havingshaft-s in bearing contact with said plates, said plates being actedupon by fluid in said chamber and by said shafts in -a manner tending toaxially separate and to tilt said plates, and iiuid pressure means forapplying force to selected por-tions of at least one of the plates forprecisely counteracting Ithe tilting forces acting on said one plate andfor preventing vaxial separation of said one plate from said gear sides.

lle. A cartridge for use in a pump housing, said cartridge comprising apair of plates having opposed recesses one of said plates being axiallymovable on said dowel means towar-d the other of said plates for closingsaid pumping chamber.

15. A pump comprising a housing, first and second plates within saidhousing and having opposed recesses forming .a pumping chamber with .alow pressure inlet zone and -a high pressure outlet zone, means forsupporting said plates within said housing, at least one of said platesbeing axially movable relative to the other, gears rotatable in saidchamber `for forcing fluid from said inlet zone to said outlet zone,fluid pressure means for forcing said `one plate axially toward theother, said recesses and gears having opposed surfaces subject toradially acting forces from fluid in said pumping chamber tending toradially displace the gears relative to the plates, said gears havingshafts in bearing contact with the plates at points axially ofset fromsaid recesses for prevent-ing such radial displacement, such bearingcontact lapplying radial forces to said pla-tes in opposition to andaxially offset from the radial forces acting on said recess surfaces,said fluid pressure means counteracting the tendency of said plates totilt due to said Iaxially offset radial forces acting oppositelythereon.

'16. The pump of claim 15 in which the recesses are of equal depth andthe gears extend the same axial distance into each recess whereby theforces tending to tilt each plate are the same.

`1'7. A pump comprising a housing, rst yand second plates within the4housing having opposed recesses therein and axially movable relative toeach other, means for supporting said plates within said housing, saidrecesses forming a pumping chamber With a low pressure inlet zone and ahigh pressure outlet zone, meshed gears within said chamber yandrotatable therein for forcing fluid from said inlet zone to said outletzone, said plates having radially extending areas respectively subjectto vhigh pressure tuid in said outlet zones and to low pressure iiuid insaid inlet zones whereby fluid pressure in said zones tends to axiallyseparate said plates, sa-id plates and gears having axially extendingopposed areas respectively subject to radially acting forces from highpressure fluid in said outlet zone and from low pressure lluid in saidinlet zone, the net etect of said radially acting forces tending toradially displace the gears toward the low pressure inlet Zone, saidgears having shafts in bearing contact with the plates at points axiallyolf-set from said opposed areas for preventing such radial displacement,such bearing contact applying radial `forces to said plates inopposition to and axially oifset from the net radial forces .acting onsaid axially extending plate areas, said axially oifset forces tendingto tilt said plates, and fluid pressure actuated means acting on atleast one of said plates to counteract both said axial separating andplate tilting lforces,

18. The pump of claim 17 in which the axes about which the -plates tendto tilt are so located that the net effect of the tilting forces tendsto move the plates in a separating direction at the high pressure zonesand in a converging direction at `the low pressure zones, and said fluidpressure means compensates for said til-ting tendency by applyinggreater `force to said one plate at the high pressure zones thanrequired for counteracting said axial separating forces at said highpressure zones and by applying less force t-o said one plate at the lowpressure zones than selected for counteracting said axial separating`forces at said low pressure zones.

19. The pump of claim v18 in which the force applied to said one plateat the high pressure zone by said fluid pressure actuated means isgreater than a force selected for overbalancing said axial separatingforce at said high pressure zone by an amount substantially equal to theplate separating force applied at the high pressure zone due to saidtilt-ing forces and the force applied to said plates at the low pressurezone by said Huid pressure actuated means is :smaller than a forceselected for overhalancing said axial separating force at said lowpressure zone by an amount substantially equal to the 4:plate convergingforce applied at the low pressure zone due to said tilting forces.

20. A pump comprising a housing, iirst and second plates within thehousing having opposed recesses therein, means supporting said plateswithin said housing, said recesses forming a pumping chamber with a lowpressure inlet zone an-d a high pressure outlet zone, meshed gearsWi-thin said chamber and rotatable therein for forcing fluid from saidsaid inlet zone to said outlet zone, dowel means for .axially aligningsaid plates, at least one plate Ibeing axially slidable on said dowelmeans toward and -away from the other plate to accommodate thermalexpansion and contr-action of the gears and plates, said Plates havingradially extending areas respectively subject to high pressure fluid inthe outlet zone and to low pressure fluid in the inlet zone whereby uidpressure in said zones tends to axially separate said plates, saidplates and gears having 4axially extending opposed areas respectivelysubject to radially acting forces from high pressure uid in the outletzone and low pressure uid -in the inlet zone, the net eieot of saidradially acting forces tending to radially displace the gea-rs towardthe low pressure inlet zone, said gears having shafts in bearingcont-act with the plates at points axially offset from said opposedareas for preventing such radial displacement, such bearing contactapplying radial forces to said plates in opposition to and axiallyoffset from the net radial forces acting on said Iaxially extendingplate areas, said axially offset forces tending to tilt said plates in amanner which would cause .at least said one plate to impose a radialload upon said dowel means, and iluid pressure operated means forcounteract-ing said axial separating forces but yieldable to permit saidaxial sliding of said one plate on said dowel means due to said thermalexpansion and contraction, said huid pressure operated means alsoc'ounteracting said tilting forces whereby lradial loading of said dowelmeans by said one plate is avoided.

v21. The pump of claim 20 in which both of -said .plates are axiallyslidable on said dowel means and said huid pressure means causescounteraction of said tilting forces on said other plate.

22. The pump of claim 20 in which said dowel means is engaged in housingrecess means at one end only of said plates for locating said plateswithin said housing.

23. A pump comprising a housing having a pumping chamber with inlet andoutlet passages, gear means rotatable within the chamber for forcingyiiuid from the inlet passage to the outlet passage, axially ymovableplate means mounted for sealing side faces of said gear means, saidplate means being acted upon at different points by -diifering iiuidpressures in said chamber urging the plate means in a direction axiallyaway from the gears, a stop for limiting movement of said plate meanstoward said ygears for establishing an initial .predetermined clearancebet-Ween the gear side faces and said plate means, a multiple of Huidpressure actuated means for urging the plate means against said stop,each of said iiuid pressure actuated means 'being acted upon by a iluidpressure corresponding to that .at a selected one of said points.

24. A pump comprising a housing, a pair of plates mounted within saidhousing, said plates having opposed recesses forming a pumping chamberwith inlet and outlet passages, gears rotatable within said housing forforcing fluid from said inlet passage to said outlet passage, saidplates sealing the side faces of said gears, atleast one of said platesbeing movable in axial directions toward and away from said gears, saidone plate being acted upon Vat different points by `differing fluidpressures in said chamber urging said one plate in a direction axiallyaway from the gears, a multiple of iiuid pressure actuated 13 14 meansfor urging said one plate toward s-aid one gear 2,593,369 4/52 Wachter103-126 with greater force than said one plate is urged away from2,728,301 1,2/55 Lindberg 103-126 said gears 'by uid pressure withinsaid chamber, each of 2,793,595 5/ 57 Lauck 103-126 said Huid pressureactuated mea-ns lbeng `acted upon by 12,876,705 3/59 Aspe-1in et tal103--126 uid from .a selected one of said points. 5 '2,880,678 4/59Hoier 10S-126 ZS. The pump -of claim 24 in which said one plate is2,967,487 1/61 Nagely 1103-126 also `subject to forces tend-ing to tiltthe same, and said 3,076,413 2/63 Hoier 10S-217 fluid pressure actuatedmeans counterbalances said ti1t- :3,083,645 4/63v Donner etal 10S-217`ing tendency. 3,096,719 7/6'3 McAlvay 10S-126 10 :3,106,166 10/63Tomasko et a1 10S-217 References Cited bythe Examiner 1,927,395 9/33Edwards 10a- 126 WIDBUR J- GOODLIN, Examiner 2,312,891 3/43 Ferris103-126

1. A PUMP COMPRISING A HOUSING, FIRST AND SECOND PLATES WITHIN SAIDHOUSING AND HAVING OPPOSED RECESSES THEREIN FORMING A PUMPING CHAMBER,MEANS SUPPORTING SAID PLATES IN SAID HOUSING, AT LEAST ONE OF SAIDPLATES BEING AXIALLY MOVABLE RELATIVE TO THE OTHER, INLET AND OUTLETPASSAGES IN COMMUNICATION WITH SAID PUMPING CHAMBER, ROTARY PUMPINGMEANS IN SAID PUMPING CHAMBER OPERATIVE WHEN ROTATED FOR FOCING FLUIDFROM SAID INLET PASSAGE TO SAID OUTLET PASSAGE, AND FLUID FROM SAIDINLET FOCING SAID ONE OF SAID PLATES AXIALLY TOWARD THE OTHER.